Boudouard’s equilibrium is established when carbon dioxide reacts with carbon. Because of reactions endothermity the temperature increase shifts the reaction rightwards and the temperature reduction leftwards.
Dynamic equilibrium is established when two opposing processes are occurring at precisely the same rate, so that there is no apparent change in the system over long periods of time.
Law of chemical equilibrium (also called the law of mass action) states that the rate at which a substance reacts is proportional to its active mass (i.e. to its molar concentration). Thus, the velocity of a chemical reaction is proportional to the product of the concentration of the reactants.
Thermodynamic equilibrium is a system equilibrium in which energy that it gains from its surroundings is exactly balanced by the energy that it loses, no matter how much time is allowed to pass.
The equilibrium constant (K) was originally introduced in 1863 by Norwegian chemists C.M. Guldberg and P. Waage using the law of mass action. For a reversible chemical reaction represented by the equation
chemical equilibrium occurs when the rate of the forward reaction equals the rate of the back reaction, so that the concentrations of products and reactants reach steady-state values.
The equilibrium constant is the ratio of chemical activities of the species A, B, C, and D at equilibrium.
To a certain approximation, the activities can be replaced by concentrations.
For gas reactions, partial pressures are used rather than concentrations
The units of Kp and Kc depend on the numbers of molecules appearing in the stoichiometric equation (a, b, c, and d).
The value equilibrium constant depends on the temperature. If the forward reaction is exothermic, the equilibrium constant decreases as the temperature rises. The equilibrium constant shows the position of equilibrium. A low value of K indicates that [C] and [D] are small compared to [A] and [B]; i.e. that the back reaction predominates.
The equilibrium constant is related to ΔrG°, the standard Gibbs free energy change in the reaction, by
Acid dissociation constant (Ka) is the equilibrium constant for the dissociation of an acid HA through the reaction
The quantity pKa = -log Ka is often used to express the acid dissociation constant.
Activity (a) is a thermodynamic function used in place of concentration in equilibrium constants for reactions involving nonideal gases and solutions. For the species i activity is defined as
where ai is the activity of the species i, ci is its molar concentration, and fi is a dimensionless quantity called the activity coefficient.
Allotropy (Gr. allos, other, and tropos, manner) is the phenomenon of an element existing in two or more physical forms in the same physical state. The difference between the forms involves either crystaline structure (white, red and black phosphorus), the number of atoms in the molecule of a gas (diatomic oxygen and triatomic ozone), or the molecular structure of a liquid (liquid helium an helium II).
In some cases, the allotropes are stable over a temperature range, with a definite transition point at which one changes into the other. For instance, tin has two allotropes: white (metallic) tin stable above 13.2 °C and grey (nonmetallic) tin stable below 13.2 °C. This form allotropy is called enantiotropy. Form of allotropy, in which there is no transition temperature at which the two are in equilibrium, is called monotropy.
Allotropy does not apply to the substance existing in different physical states as, for example, when ice melts and changes from solid ice to liquid water.
Allotropy is generally restricted to describing polymorphic behaviour in elements, while polymorphism may refer to any material having multiple crystal structures.
Free energy is an energy that is actually available to do useful work. A decrease in free energy accompanies any spontaneous process. Free energy does not change for systems that are at equilibrium.
Grignard reagents are organomagnesium halides, RMgX, having a carbon- magnesium bond (or their equilibrium mixtures in solution with R2Mg + MgX2).
Generalic, Eni. "Boudouard%E2%80%99s equilibrium." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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